In criminal cases, a clear, secure and verifiable chain of evidence is important to achieve successful prosecution of an accused. There are many high profile cases where the mishandling, misplacement or loss of evidence items resulted in the refusal of the authorities to charge a suspect, the dismissal of charges by the judge, or a conclusion by the jury that the charges were not proven beyond a reasonable doubt. Conversely, there have been cases where accused persons may have been unjustly prosecuted or convicted by tainted evidence.
In order to be admissible in court, physical evidence that relates to the issues in a case must be verifiably authentic in order to avoid attack by the parties and exclusion from consideration. Thus, for example, in a criminal case, physical custody of a piece of evidence is carefully documented. In practice, this means that a police officer or detective typically documents the collection and takes charge of a piece of evidence, followed by transfer of the evidence to an evidence clerk for storage in a secure place. These transactions, and every succeeding transaction between the collection of the evidence and its appearance in court, are typically extensively documented chronologically to maximize the ability to withstand legal challenges to the authenticity of the evidence.
Chain of custody may be established with the execution of appropriate evidentiary procedures by those responsible for maintaining the integrity of evidence after collection. However, in some situations, it may be challenging to establish the integrity of evidence collected outside of the presence of police or other relevant authorities. It is nonetheless important for such evidence to be capable of being authenticated to ensure its admissibility or acceptability.
An example of evidence where collection may be problematic is that obtained from tracking devices used for security and related purposes, such as to track currency stolen in a bank robbery. Often, the teller may give the criminal a tracking device disguised as a banded stack of currency bills along with standard wrapped currency. This tracking device is capable of communicating its GPS location to a remote monitoring station as it is being transported by a criminal.
When the tracking device is in communication with a cellular network, information regarding the tracking device location, temperature and the like is typically received at a remote location substantially in real time, or without significant delay. Frequently, however, the tracking device may travel through a location that does not have a strong cellular signal or that does not have a cellular signal at all, that is; the tracking device and its associated asset—here stolen currency—may enter a “dead zone.” Alternatively, the tracking device may lose cellular coverage through deliberate action of a person, such as by shielding or blocking of the signal using known means. In such situations, information regarding the handling of the tracking device may still be generated if the satellite signal is still received and the onboard sensors are still active. However, the absence of a cellular signal prevents the information from being transmitted in real or substantially-real time or without significant delay.
Typically, the tracking device is configured to retain information acquired during a dead zone as data that may be stored on the tracking device until the memory is full, at which time additional information may be retained by writing over the earlier data, thus leaving only the later-collected information to be transmitted as data messages when the cellular signal is restored to the device. This results in a tracking device dataset that may not provide information regarding a substantial aspect of the paths travelled by the tracking device from the start of the tracking event to the recovery of the tracking device by the authorities. Accordingly, the dead zone event and lack of consistent data associated therewith may reduce the usefulness with respect to evidentiary reliability of the entire set of data acquired during the tracking event.
As an alternative to writing over data, memory on a tracking device may be conserved if less information is collected, such as by spacing out the time between data acquisition and therefore collecting fewer data points. While this may be an effective method to collect information data when memory size constrains data archiving capability, in order to be used for evidentiary purposes, tracking device information more ideally provides sufficient detail to be accepted as proof of the handling and travel of the tracking device (and its associated asset) during the tracking event. This is especially true when the tracking device is in transit during the tracking event, as may occur, for example, when a robber is fleeing the scene of the crime to evade capture. In such cases, reduction in the frequency at which tracking device information is collected and/or recorded for storage may result in a significant loss of information about the exact path the tracking device traveled and whether the person handling the tracking device stopped along the way. Such stops may signal that a thief off-loaded the currency or other tracked asset or that the identity of the persons handling the tracking device changed. Absence of such information could result in questions being raised about the integrity of the evidence obtainable from the tracking device and, in some cases, lead to inadmissibility of the evidence in a court. Alternatively, incorrect identification of the persons in possession of the tracking device at various times during the tracking event may result in the incorrect persons being prosecuted.
Problems associated with the amount of memory needed for collecting and reporting evidentiary quality tracking device data cannot reliably be solved merely by adding memory modules in the tracking device. Due to the small footprint required to enable tracking devices to be hidden from detection, memory modules are preferably kept as small as possible. This means that, in most circumstances, memory modules cannot merely be added to create additional capability to collect tracking device data just in case the cellular signal is lost during use. Even for applications permitting larger tracking devices to be suitably hidden, such as in an ATM safe, additional memory modules may unacceptably add to the complexity and cost of the tracking device. Irrespective of the size of the memory module in the tracking device, if the length of time that the cellular signal becomes long enough, at some point, the memory capacity of the tracking device may become full.
Thus, there remains a need for methods and devices to enable obtaining evidentiary-quality data from tracking devices associated with assets in need of tracking, even if the device loses communication with a cellular tower for one or more periods during a tracking event, such as a robbery, theft or other event.